Learning Goals
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To understand the basic structure of DNA
To become familiar with the proper
vocabulary related to DNA and the cell
cycle
To understand the key stages of the cell
cycle
To understand the purpose of mitosis
To understand the key steps in the phases
of mitosis
DNA (Deoxyribonucleic Acid)
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The material that contains all of the cell’s
genetic information
Let’s take a closer look at the structure of DNA…
The Structures of Genetic Material
The Cell Cycle and Cell
Division
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In multicellular organisms cell
division is required for …
1. growth of the organism
2. repair of tissues and organs
3. maintenance to replace dead cells
Cell Division and the
Cell Cycle
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Cell division requires the distribution of
identical genetic material (DNA) to two
daughter cells.
“Biology – the only science where division and
multiplication mean the same thing”.
The Cell
Cycle
A controlled
process of
growth and
division
Regulated by
checkpoints
Interphase-
during interphase the cell carries
out its normal functions, as it grows and makes
copies of its genetic material.
Stages of Interphase:
G1: major period of
growth.
S phase: DNA (chromatin)
is replicated.
G2: further growth and
production of molecules
Mitosis- the separation of the cell’s replicated
genetic material
Phases: Prophase, Metaphase, Anaphase,
Telophase
Cytokinesis:
division of the
cell’s cytoplasm
and creation of
new cells
Before we take a closer look at the
stages of the cell cycle, let’s review
some key terms…
Chromosome

A single linear DNA molecule; once the
chromatin has condensed it is known as a
chromosome
Sister Chromatid
•
one of two chromosomes that are genetically
identical (formed when the DNA replicates)
Centromere
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The structure that holds the chromatids together
Spindle Fibres
•
Facilitate the movement of chromosomes within
a cell
Centrosome
• a structure that helps to form the spindle fibres
Late Interphase
(S Phase)
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During S phase of
interphase the cell must
make an identical copy
of its DNA.
Why is this
necessary?
Late Interphase
(S Phase)
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This is necessary so
that each new
daughter cell has a
full set of
intructions.
Also during this stage
centrosomes
duplicate, and begin to
organize spindle fibres
Prophase
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chromosomes are tightly
coiled, with sister
chromatids joined
together at centromere
nucleoli and nucelar
envelope disappear
mitotic spindle begins
to form and attach to
chromatids at centromere
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Metaphase
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spindle fibers push the
sister chromatids until
they are all arranged at
the metaphase plate (an
imaginary plane in the middle
of the cell)
Anaphase
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Sister chromatids
separate
each is now pulled
toward the pole to which
it is attached by spindle
fibers
by the end, the two
poles have equivalent
collections of
chromosomes
Telophase
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cell continues to elongate
two nuclei begin to appear,
as new nuclear envelopes
form
chromatin less tightly coiled
cytokinesis, division of the
cytoplasm, begins
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Cytokinesis, division of
the cytoplasm, typically
follows mitosis.
In animal cells, a
cleavage furrow forms
in the cell surface near
the old metaphase plate.
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Cytokinesis in plants, which
have cell walls, involves a
completely different
mechanism.
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Instead of the cell pinching
inward, a cell plate forms
along the centre, eventually
creating a new cell wall
between the daughter cells .
Phases of
Mitosis